Twitter CEO Dick Costolo has repeatedly protested that Twitter doesn’t see itself as a media entity and doesn’t want to be one, and there are some obvious reasons why the company wouldn’t want to be seen that way, including the fact that it has been spending a lot of time negotiating partnerships with existing media players such as ESPN. It would likely be a lot harder to make the case that media companies should see the service as a partner if Twitter was promoting itself as a media company (Costolo may also be concerned that media companies don’t typically get nosebleed valuations the way tech companies do).

Until recently, Twitter was just a platform that provided easy access to this real-time content created by others. But deals like the NASCAR partnership — and offerings like the email summary powered by its Summify acquisition — are pushing Twitter further and further into the “curation” business, and that is essentially an editorial function.

Selecting tweets and photos about a car race might not seem like journalism, but what Twitter is doing is very similar to what a site like Huffington Post or even a newspaper or sports site might do with an event like NASCAR. A traditional media outlet might also have a columnist write some thoughts about the race as well or send a reporter down into the pits to interview drivers, but pulling together real-time reactions from those involved and from spectators has also become a big part of the media response to a major event.

The most compelling reason for Twitter to move into this kind of area is that it could increase the engagement that users have with the network, something that is fairly crucial when it comes to appealing to advertisers. Being a platform and allowing anyone to distribute content through your network is great — but coming up with reasons why users should spend time on your pages (and look at the ads) is also pretty attractive from a business point of view. Can Twitter do both at the same time? Can it offer itself as a partner for media companies while also tip-toeing into the editorial end of the business?

If nothing else, the Twitter deal with NASCAR reinforces the fact that for traditional media companies, competition is everywhere — just as Twitter itself can hire editors to curate and aggregate content, so brands and advertisers like the auto-racing entity are becoming publishers and content creators in their own right, with all the same tools that media outlets have at their disposal. Everyone is a media entity now.